Automatic telephone-exchange system.



J. W. LATTIG 6: G. L. GOODRUM;

AUTOMATIC TELEPHONE EXCHANGE SYSTEM.

APPLICATION FILED SEPTJG, 190a.

920,350. Patented M y 4, 1909.-

I 2 BHEETB-SHEBT 1. Kl

Ufi l'ne sses.

J. W. LATTIG & G. L. GOODRUM. AUTOMATIG TELEIHONE EXCHANGE SYSTEM.

APPLICATION FILED SEPT. 16. 1903.

' Patented May 4, 1909.

2 SHEETS-SHEET 2.

NESSEIS: WK B m I Kfrziu spectively, of lr 50 lays,

BEST AVAlLABLlS COPY JACOB WILLIAM LAJTIG, OF WYNCOTE, AND

PENNSYLVANIA, ASSIGNORS TO THE AMERICAN AUTO ROCHESTER, NEW YORK, A CORPORATION.

CHARLES LANE GOODRUM, OF PHILADELPHIA, MATIC TELEPHONE COMPANY, OF

AUTOMATIC TELEPHONE-EXCHANGE SYSTEM.

Specification of Letters Patent.

Patented May 4, 1909.

wi t l Application filed September 16, 1903. Serial No. 173,400}. [b U To all whom it may concern: Be it known that we, JACOB WILLIAM LATTIG and CHARLES LANE Goonnun, citizens of the United States, and residents, re-

and Philadelphia, Philadelphia county, Pennsylvania, have invented a certain new and useful Improvement in Automatic Telehone-Exchange Systems, of which the follo "owing is a specification.

Our invention relates to automatic exchange systems oomprlsing that class of telephone systems wherein no operators are reqluired "to manually make connections and ear out the same, this work being done entirely by niechanisnts located at a central oi fice and controlled by transmitting mechanism at the subscribers stations. Heretofore it has been "founddiflicult to arrange systems of this class to operate without individual batteries, and to centralize, as well as unify the sources of energy as has been done in connection with manually operated. equipments.

It is the object of our invention to produce an automatic telephone system using centralized battery, whence energy may be derived for selective purposes and for the transmitters, and also a centralizedsouroe of ringing current automatically controlled.

It will be understood that the principles underlying our present invention may be applied to any automatic exchange system, the fund rental or basic requirements being the sai e in every case, viz: that the subscriber may be able to produce current in.- pulses or variations in his circuit to ell'ect relays or controlling magnets to produce a conjunction of connecting apparatus from.

40 his own line terminal to that of the line wanted. The invention is applicable to such systems as the Strowger automatic, whicl'i is now in commercial use. li e show herein however, a skeleton outline of a systern and apparatus which may be taken as typical only, conventional form being used for the switches.

Our invention consists essentially in the use of two diiferentiallywound selecting re and a neutral restoring relay which acts in conjunction with one of them together with a main battery at the central office connected parallel. through the differential yncote, Montgomery county,

i I i l I j l l l relays to the various lines entering the exchange. This battery is grounded at a point intermediate of its end cells and nearer to one end than the other, so that as between the ground and one line wire there will be a greater potential difference than exists betery is bridged across the connected circuits' through the differential relays, and no effect is produced upon the connecting or disconnecting magnets until the subscriber hangs up and intentionally restores.

Our invention is illustrated in the accompanying drawings wherein Figure 1 is a diagrammatic View of a systern embodying the invention, andFig. 2 is a similar view illustrating the system as applied to control the movements of the switch mechanism of the aforementioned Strowger automatic system.

Similar reference characters in the several figures indicate similar parts.

To facilitate an understanding of the operation and function of the various parts of a system embodying our invention we have illustrated it in connection With one of the several types of switches employed in connection with the Strowger automatic tele phone system, a coin )lete description of which appears in Unite States Letters Pat-- out No. 591,201, granted October 5th, 1897 to A. B. Strowger at at. However, as our present invention relates to means for controlling the operation of the switch we have only shown the parts of said switch with which said means cooperate, it being understood that the remaining parts thereof such as those connecting difl erenttelephone lines, operate'as dcscribei'l in the afmenientioned patent.

The operating mechanism of "he switch shown in Fig. 2, comprises a main operating shaft 200 which-is so so ported that it is normally free to both re'vo ve and slide longitu- (finally. Secured to the shaft 200 is an elongated ratchet wheel 80 having teeth so arranged on the main portion thereof that by l only,

ringer and bridges the talking set.

virtue of a magnet,- a lever 110 and pawl 111, the shaft may be revolved in one direction step by step. Thereis a .detent 8 which serves to retain the ratchet wheel in position after each successive thrust of pawl 111. Secured to the shaft 200 is a ratchet cylinder 151 provided with circumferential teeth racked in one direction which may be en- LO gaged at any point by a pawl 161 when impelled by virtue of a magnet through a lever 181, this being the means of imparting a longitudinal step by step movement to the shaft 2. There is a os't.16 which serves the double purpose of a stop, against which the free end of pawl 161 contacts to limit its movement and also to hold the pawl in inoperative position when the shaft 2 is to be;

returned to its normal position, as will be understood. There is a detent 191 for retaining the ratchet cylinder-151 with the shaft 2 in the desired position after the thrust of the pawl 151. A groove 37 (shown in dotted nes) is cut at one side of the ratchet cylinder 161 so that when the latter is in one position, the stop pawl. 191 is out of engagement with the notches of ratchet 151, which permits of a free longitudinal movement of the shaft 2 in either direction. The detent 8" is attached to an oscillatory shaft and is rocked out of engagement with the ratchet wheel 80 to release it at the proper'tinie.

A and A are two subscribers 'stations, connected with the central office by the line nected by the mechanism operated by the switch shaft'200. At each station we provide the usual apparatus for talking, comprising the transmitter T and the receiver 1, together with a ringer Q. The bridge 14 containing the talking set is normally open atthe switch hook, while the bridge 15 containin the ringer Q and a condenser C is norma ly closed at the switch hook. In addi-tion to this apparatus we provide each line wire with a grounding key which may be-a plain key or push button as shown at K-K, or may be a spring contact or the like controlled by suitable mechanism for transmitting selective impulses.

' The main battery B may conveniently be composed of thirty cells of accumulator, giving about sixty volts between the. end ternnnals,and we divide it into two portions by the ground wire 1, with ten cells on one side and twenty on the other, so that the portion 7) will give forty volts and the portion 1) will give twenty volts.

7-10 is a subscribers line passing from the substation A to the central office. At the subscribers station the usual transmit ter T, receiver T, switch hook H and ringer Q, are provided, to ether with a condenser C. The switch hook normally maintains the circuit complete to the condenser and ringer central office apparatus.

wires 7-10, the latter being the station con-- lay maintained in a but when raised in use it cuts out the In the diagrammatic illustrations SM and SM are the selectormagnets of a Strowger ASSUIILlHg the subscriber whose ine is shown in the figure 'to be connected with a one hundred line exchange, these magnets by cooperative ef-= fects determine the position of the mechan ical switch arm connected to the shaft 200 constituting his line terminal, with respect to any of the hundred pairs .of' contacts in his selector switch by the conjoint operation of movingsaid shaft longitudinally and rotating it. In order to control these movements and this position of the switch arm the subscriber must be able to energize either or both of these magnets as occasion may require.

RM is the usual restoring magnetof the Strowgersystem. When this magnet is energized the switching mechanism is permitted to-return to an inoperative or zero position R and R are two differential relays, which may be of any convenient type. Each relay is permanentlypolarized and has a soft iron pivoted armature adapted to move one way or, the other between the polar extremities N and S as it is polarized one way or the other by current in its res ective windings. The armature r of relay has windings r and r, and plays between contacts 1" and W. The other relay. R has windings r and r u on its armature 1' which is adapted to c ose upon contacts r and r. A neutralr'elay R is connected in series with the'winding r of the relay R, and as it is desired to have the windings on both sides of each rebalance'd condition, an impedance coil I is included in series with the other winding r being given the same resistance and the same magnetic coefficients as the relay R -Line wire 7 has the. grounding key K, and line wire 10 has a similar grounding key K Line wire 7 passes to the central ofiice and there is co inected in series through and with the relay R the winding r of relay R the winding 1 of relay R, one division I) of the 11% main battery B and to ground. Line wire 10 likewise passes to the central office and there in series to and through the impedance coil I the winding 1 on relay R the-winding 1" on relay R, and the other division b'of the 12 1 nain battery B and so to ground. The selector magnet SM is connected with the 16- cal circuit 18-19 containing a battery B and controlled by the armature r and contact r. The relay SM is included in the local circuit 16-17 with the battery B and controlled by the armature working on contact 1- The restoring magnet RM is included in the local circuit 20-21-22 including a battery B and controlled at two act No. 3 is the points, one by the armature 2/1 of the relay l winding 2*, wire 2, battery division b, wire I i and ground. ui'rcnt flowing through this ll", and the other by the armature. i" of the relay R. working on the contact r We will now give the operation of the ap paratus so far described, assuming the system to be completed by the addition of all the required Strowger apparatus, as shown in Letters Patent No. 591,201. With such apparatus three movements or acts are necessary, involving impulses over the subscribers two line wires and the ground or return wire. It is of course understood that in all common battery telephone transmission there must be a constant difference of potential between the two wires, and between the terminals of each transmitter; and in our system we must maintain this condition, and in addition we must do so without interfering with the consummation of the three acts, and Without permitting them to interfere with the constant potential differences. Movements Nos. 1 and 2 may be designated as selector and connector movements, being performed by the magnets SM" and SM?. These may of course be. continued from one selector to another indefinitely, as will be fully understood by those skilled in the art and familiar with the Strowger system. Movement or releasing movement to which we have referred and is performed by the magnet RM. Upon inspection of-the diagran'is it is apparent at a glance that the main battery B is bridged. to maintain a constant potential difference between the line Wires 7 and 10 Supposing now the subscriber in calling desires to make the first selector movement; he depresses key K, which completes a circuit from ground at the subscriber's station by, wire 11 to key K, wire 10,

impedance coil I, wire 9, winding 1' wire 5, winding r, Wire 3,. battery division I), wire 1 and ground. The direction of the current flowing in this circuit is such that the armature r 'of-the relay R will be properly polarized to close up'on its contacts r and 1*; but the relay R Will not operate, being oppositely polarized. The operation of relay R'closes the'circuit18 19 containing the ma net SM, whereupon this magnet is energize by current from battery B and makes the first step in the selection, which may be repeated as often as desired by the continued manipulation ofthe subscribers key K. It will be observed that When-the armature 1" closes the circuit 1819 it also closes its break in the circuit 20 2122 containing the release magnet RM. The latter does not become energized,however, because the second break at m is not closed, the neutral magnet R being connected with the line wire 7 and therefore receiving no current. The second movement is attained by the use of the key K, whose depression produces a closure of a circuit from the ground by wire 8, key K, wire 7, magnet R wire 6, winding r, wire 4,

in the figure.

circuit from the battery division 0 is op- Jositc in direction to that previously traced, and it finds the armature r" properly p0lar ized to respond by closing the circuit 16*17 containing the second magnet 5M whose armature s" performs the second or connectivc act in the mechanical movement. relay R is not operatively energized, but it will be observed that theneutral relay receives current. The circuit 20 2l-22 remains open, however, at the Contact T The movement of the magnet 8M may obviously be repeated as often as desired by repetition of the key movement. The selector and connector movements having been satisfactorily performed, the subscriber takes down his receiver T, when the switch hook H immediately bridges the transmitter and receiver across the linewires 9 whereupon current will flow tallic circuit from the main battery B by the following path: wire 3, winding r, wire 5, winding 1", wire 9, impedance coil I, line Wire 10, wire 13, switchhook H, wire 14,receiver T and transmitter T, wire 12, wire 7, magnet R wire 6, windingfi, wire 4, winding 1*, wire 2 and battery. It will be understood that the extensions and 100 of the two line wires pass to the contacts of the selective a paratus, both of the present subscriber an of other subscribers, as will be sufliciently apparent from a study of the patent to which we have referred. (Jonse uently when the connection is established by the successive acts we through the me- .have described the line 7-10 becomes connected through the said extensions with the line 7 and 10 of another subscriber A, the connection being indicated by dotted lines The battery B is therefore bridged across the two connected metallic circuits at the oin ts a; y, and in the bridge are included tie coils I and R whose impedance chokes back anyflvoice currents that might otherwise pass into the bridge and hence to other lines by the various connections indicated at Z, the battery being common to the exchange. The differential relays may be disregarded, as their windings balance each other, so that we have a plain bridged battery with impedance coils, giving an ideal central energy circuit.

When it is desired to clear out, the subscriber depresses both keys KK, or in angiiig up his telephone the same effect may be produced by an automatic mechanism, either mechanically on the keys, or electrically by closing the two ground wires 8.

and 1 The effect of this double closure is to produce currents siimiltaneously in both line wires 7 and 10 from the two sides of the battery b and I). These currents are opposite in direction and unequal as to strength, and the inequality and 10,

being in favor of the side Theill)

- to normal or zero posi -central battery may ine wires impulses of might be caused points r and r, the former thus closing one break in the circuit 20-2122. The current in line Wire 7, while insufficient to produce any effect upon the selective magnets energizes-the magnet R and thus closes the other break at m, whereby the magnet RM isenergized to release the switching mechanism, and the entire apparatusis restored erative until another call.

In a systemembodying our lnvention a operating themain switching apparatus, and

andby arranging the circuits in the manner shown, current in ulses-may be transmitted over the separate to effect the different operations of the. central office switching apparatus or current may be despatchedoyer for restoring said apparatus. c

It is well understood that as'far. as 'pos- 25v both line wires. to form acompound circuit sible grounds should notbe present on anyv part of a telephonetc ircuit, and in case of'a.

common battery system in particular the total destr'uctionofa balance on many lines by grounds on one or a few by reason of their all being tied together. at the battery terminals'Z. In our system it will be noticed that the" lines are only grounded at the subscribers ,stations for brief eriods and for selective purposes, the meta 'c circuits being free from grounds normally, except for the single ground wire 1 on the main battery, and as the batteryis of very low internal resistance, this ground may be considered at a neutral point-of the entire system, where it is incapa le of doing any harm.

I system,

Having thus described our invention, what we claim and desire to secure by Letters Patent of the United States is? 1. In an automatic telephone exchange a central station, subscribers stations and metallic circuits connecting the central station to the respective subscribers. stations, switching ated devices, a source 9f current supply con nected in common to a plurality of subscrib ers circuits to furnish energy both for the automatic control of the switching apparatus and means whereby a constant difference of poand for the subscribers transmitters,

tential in the current supply may be main tained across said particular circuits for telephonic vtransmission purposes, and means also whereby variable potential difierences in the current supply may be determined over the subscribers line and between a subswitching apparatus at tion, to remain mop' be employed to furnish current both for selective purposes, such "as station, central station apparatus at the central" station embodying electromagnetically-oper-' scribers apparatus and the electromagnetic devices of the central oflice' switching appar-atus-for operating the latter. 2. In an automatic telephone exchange system, a central station, subscribers stations and a metallic circuit connecting each subscribers stationwith the central station common sourceof supply at the central station connected to the subscriberscircuits and to the central station switching appara tus, maintaining a constant potential difference on-each subscriber s line for transmitter thecentral station, a

purposes, together with means 'for producing .a difierence in polarity. over the separate subscriber's line wires for actuating and restor ing. the switching apparatus. a

3. In an automati "telephone exchange system, tions and a metallic circuit interconnecting eachf subscribers station with the central station,- switching apparatus at the central station; a-conmaon source of supply at the central station connectedin its'entirety to maintain "amaximum .potential difierence' across each subscribers'circuit, and connected sectionally and unequally to the central station switching apparatus,

determine a currentflowacross any given circuit for transmitter purposes, and separately to control the flow of current from the divisions or sections of" the main battery to the switching apparatus to control the opera-v tionof the latter-..

4', In aniautomatic telephone exchange system, a central station, subscribers stations and a metallic circuit inter-connectin each'subscribers station with the centra station, switching apparatus at the central a common source of supply at thebridged' across a subscribers circuit whenin nearer one ole than the other, with connec tions from oth poles of the'source to the switching apparatus, and means at the subscribers stations for connecting the telephone sets in metallic circuit, and means also for grounding the individual line wires whereby the automatic operation of said switching apparatus may be controlled.-

t5. In an automatic telephone exchange system, a central station, subscribers statrons, and a metallic-circuit connecting each subscribers station with the central station, switching apparatus at the central station, controlling magnets therefor, a source of current supply connected in common. with all the lines both for operating the subscribers transmitters, and the controlling magnets, connections from opposite sides of the source of current to said magnets and a ground connection on the source from a point interme-- 'a central station, subscribers sta-' together with means atthesubscribers"v stations, to

use and grounded ata pointj ducing a flow of may be produced on opposite sides of the central station controlling magnets to affect the l station with the switching apparatus.

6. I central station, subscribers stations and line circuits interconnecting them, a central station switching apparatus and difl'erential controlling magnets therefor, acommon source of current, means at the central station whereby a constant difference in. potential may be produced by said source across the terminals of the subscribers transmitters, and means at each subscribers station whereby unequal differences of potential may be produced across the terminals of the controlling magnets at the central station.

7. In an automatic telephone exchange system, a central station, a subscribers sta- -tion and a line circuit interconnecting them,

a switching apparatus at the central station and a plurality of differential controlling magnets therefor, a source of current, means at" the central station whereby said source may be caused to maintain a constant potential difference across the subscribers telephone terminals, and means at the subscribers station whereby unequal differences of potential may be produced between themagnets.

terminals of the several controlling 8. In an automatic telephone exchange system, a central station, subscribers stations, and line circuits interconnecting them, a common source of current at the central station, a'line switching apparatus and differential also at the, central station, a connection from the source to ground from a point nearer one pole than the other, and connections from the source to the ma nets and to the lines wherey current may e supplied to the latter for the transmitter and for switching purposes, means at the subscribers stations for procurrent from the unequal central station source through the central station controlling magnets in reverse directions to actuatethe switching apparatus.

9. In an automatic telephone exchange system, a central office, subscribers stations and metallic circuits interconnecting them, a line switching apparatus at the central oflice, having magnetically-operated controlling devices, local circuits therefor and polarized relays controlling said circuits, a common source of current at the central ofilce groundand ed. at a point nearer one pole than. the other connected to the subscribers lines to maintain a potential difference across the same for transmitter purposes, connections from said source to the polarized relays, and means at the subscribers stations for causing a flow of current in the ground and metallic circuits separately or together. y

10. In an automatic telephone exchange system, a centralstation, subscribers stations polarized controlling magnets therefor I and metallic circuits connecting the central 11 an automatic telephone system, a

.plying current to the individual subscribers stations, a line switching apparatus at the central station, operating magnets therefor, polarized controlling relays for said magnets, a common source of current having its terminals connected to-opposite sides of the subscribers circuits and also to the said said source having a ground connection intermediate of its terminals, together with means at each subscribers station to cause a flow of current in the metallic circuit for transmitter purposes, and means for also grounding the individual line wires to transmit current in either or both of said line wires to control the polarized relays.

11. In an automatic telephone exchange system, a central station, a subscribersstation, a switching apparatus at the central station comprisin ma two line wires of t e su a source of current at the central station supmeans at the subscribers station to supply current from unequal portions of said source for controlling the switching apparatus.

12. In an automatic telephone exchange system, a line switching apparatus, a sourceof current unequally divided andgrounded between the divisions, and a metallic circuit connected to the switching apparatus, an actuatingmagnet and a restoring magnet for the switching apparatus controlled through opposite sides of the metallic circuit,':two polarized relays also controlled through said circuit, and a neutral controlling relay for the restoring magnet connected on the same side as the actuating magnet, and rendering the restoring magnet operative when energized,

relays,

nets arranged the scr bers OlICLlll), andsubscribers line and and whereby current through either side of the metallic circuit alone will fail to restore, but current through both the restoring magnet.

13. In an automatic telephone exchange system, a central station, subscribers" stations and individual metallic circuits therefor, a line switching apparatus at the central station comprising vertical and rotary magnets and a restoring magnet, a pair of oppositely polarized relays difl'erentially wound, a common source of current for all the circuits having its oppositeterminals each connected through a similar winding on one of the polar relays to one side of the said several subscribers circuits, a controlling relay for the restoring magnet, a circuit for the said restoring magnet and the Vertical magnet closed by one of the sage of current in one direction therethrough, anda circuit for the rotary magnet and the said controlling relay closed by the other polar relay on the passage of current in the opposite direction, together with a ground connection from an intermediate point on sides will energize I both polarized the'source of current and means at each sub scribers station to ground either or both of the individual wires of the metallic circuit. 14. In an automatic telephone exchange system a central station, subscribers stations. and individual metallic circuits therefor, a line switching apparatus at a central office,

actuating magnets and a restoring magnet for said apparatus and a controlling relay for the restoring-magnet, a pair of difierentially wound oppositely polarized relays and a common source of current having its termin'als connected each throughone winding on relays, said source being also connected in arallel through the various windings; of t e polarized relays to and across the various subscribers metallic circuits, a ground connection from said source energized, and when the other line wire isgrounded the other actuating magnet will be energized, the restoring magnet remaining inert, whereby the switching mechanism is operated, but when both line wires are grounded both the controlling relay and the restoring magnet receive current to restore the switching apparatus.

15.. In an automatic telephone exchange system, a central station, a subsc'riberssta tion and a metallic line circuit interconnecting them, a line switching mechanism atthe central station and a' pair of oppositelypolarized controlling relays therefor having a switch-restoring device controlled thereby, a source of current at the central station having its terminals connected through similar windings on both polar relays to opposite intermediate point grounded so as to divide the source-into two unequal grounded sections, means at the subscribers station to connect a telephoneset across the metallic circuit to derive transmitter current therefrom without grounding the individualwires,

fected, and means also at the subscribers "station to ground either or bothof the individual line wires at will, whereby the groundwill cause aflow of current in one direction to actuate one polar relay and the grounding of the other line wire will cause a flow of current in a reverse direction to actuate the other,polar relay, but the grounding of both line wires will cause unequal and opposite currents to flow, producing a resultant effect of sufficient magnitude to cause the actuation of one only of the polar relays to restore the switching a paratus.

In witness w iereof, we have hereunto set our hands this fourteenth day of September, A. D. nineteen hundred and three, in the presence of two subscribing witnesses.

JACOB WILLIAM LATTIG. CHARLES LANE GOODRUM'- Witnesses MARY C. MCCARTHY,

M. S. LEWIS.

sides of the subs'cribers circuit and having an;

alanced differential windings, together with wherebythe polar relays will remain unafing of one wire at the subscriber's station 

